1. Field of the Invention
The present invention relates in general to a peripheral device for a portable electronic device. In particular, the present invention relates to a peripheral device for controlling power in a portable electronic device.
2. Description of the Related Art
Portable electronic devices have power-saving capabilities, such that they can enter a power-saving or sleep mode automatically if unused for a preset time. A restart key or sequence on the portable electronic device must be used to restore the active mode. However, users may use many types of peripheral devices (such as external keyboard or joystick). In some cases, restoration is unavailable without returning to the restart key or sequence on the portable electronic device and possibly even disconnecting the peripheral device is needed.
A connection pin of a transmission cradle in the portable electronic device comprises (a) High Speed Interface (HSI) pin and (b) transmit data/power (TXD) pin. When the portable electronic device is in sleep mode, the HSI pin maintains a high voltage. When the portable electronic device is connected to the transmission cradle and a xe2x80x9csynchronous keyxe2x80x9d is pressed, the HSI pin is connected to ground and the voltage goes to 0V to drive or woken the portable electronic device. Then, the portable electronic device enters normal operation or work mode to start the synchronization procedure. When the portable electronic device is in sleep mode, the TXD pin maintains a low voltage. During data transmission between the portable electronic device and the transmission cradle, the TXD pin maintains a high voltage. The TXD pin is taken as a power source with a 2.7V output voltage and a 3 mA maximum current.
There are 2 steps needed, when a portable electronic device switching from sleep mode to work mode. 1. Input an applied signal with low voltage to the HSI pin, 2. The portable electronic device need a period of time, for example 400 ms, driving the device into work mode. 3. The TXD pin of the portable electronic device starts to supply power to the peripheral device. However, there is no power supplied from the portable electronic device to the peripheral device for about 400 ms. That may possibly cause the peripheral device unstable.
Accordingly, the object of the present invention is to provide a peripheral device for a portable electronic device. The peripheral connecting device in sleep mode is woken by input from the peripheral device without pressing a restart key on the portable electronic device.
To the above purpose, the present invention provides a peripheral device for controlling power in a portable electronic device. The peripheral device is coupled to an output port of the portable electronic device to control voltages of a first pin and a second pin. The peripheral device can detect the voltage of the second pin to determine if the portable electronic device is in sleep mode or in work mode. The peripheral device comprises an input device controller and an interface circuit.